Tuleap should warn users of very old versions of Chrome and Firefox they should upgrade.

We should warn the users for multiple reasons:

• it is not a good thing for their security to use an unsupported critical software that browsers are nowadays so we should nudge them (and/or their IT department) in the right direction
• it can be a source of frustration for them because they might encounter unexpected bugs in Tuleap 🐛
• it can generate an unnecessary consumption of resources 🌱 (e.g. users of old versions of Chrome are able to use the new list picker but does not have the support for the lazy loading of images, they can end up loading a lot of user avatars they do not need)
• it can negatively affect the performance of up to date browsers since under some circumstances we (Tuleap developers) can be forced to ship additional code and to polyfill features

The proposal for the beginning of this year is to warn users of Chrome and Firefox older than the first release of the current Firefox ESR version. This means displaying a modal for Firefox < 78 and Chrome < 84. This is a voluntarily conservative choice since Tuleap is only supporting the latest version of these two browsers. A stricter approach might be counterproductive since we want to gently push users/IT departments in the right direction. Updating those versions can (and should) be done regularly.